Content Curator
Thiourea is an organosulfur compound (organic compounds that contain sulphur) with the formula SC(NH2)2. In other words, Thiourea is a sulphur analogue of Urea. It is structurally similar to Urea – an organic compound, except that the Oxygen atom is replaced by a sulphur atom, but the properties of Urea and Thiourea differ significantly.
| Table of Content |
Keyterms: Thiourea, Sulphur, Urea, Oxygen, atom, organic compound, Thione and Thiol
Importance of Thiourea
[Click Here for Sample Questions]
It plays an important role in the construction of hetero-cycles, the compounds formed by the insertion of one or more, similar or different hetero-atoms (other than carbon or hydrogen atoms) in different cyclic systems. It appears as white crystals which are combustible and in contact with fire give off irritating or toxic fumes. It acts as a precursor to sulphide to produce metal sulphides like mercury sulphide.
Thiourea is a reagent in organic synthesis, a special branch of chemical synthesis, and is concerned with the construction of organic compounds via organic reactions. "Thioureas" can refer to a broad class of compounds with the general structure (R1R2N) (R3R4N) C=S.
Thiourea is also called by names such as “Thiocarbamide, and Pseudo thiourea”
Thioureas belong to thioamides, a functional group with the general structure R–CS–NR′R″, where R, R′, and R″ are organic groups. Examples include RC(S)NR2, where R is methyl, ethyl, etc.
Structure of Thiourea molecule
[Click Here for Sample Questions]
Structure of Thiourea molecule is shown below:
Structure of Thiourea
Thiourea exists in two forms – Thione and Thiol.
Thione and Thiol
Thione form is found in more amounts in aqueous solutions. Thiol form is also known as is thiourea.
Thiourea molecule has a planar structure. It is a covalent compound with a double bond between carbon and sulphur. C=S bond distance in Thiourea is 1.71 A and the average of C-N distances is 1.33 A. (Bond Distance is measured in Angstroms denoted by A)
Read more: Classification of Organic Compounds
Properties of Thiourea
[Click Here for Sample Questions]
Thiourea shows the following physical and chemical properties:
- It is an organic compound containing sulphur atoms.
- Its molar mass is 76.12 g.mol-1.
- It is a white-coloured compound.
- It exists in a solid state at room temperature.
- The melting point of thiourea is 182o.
- Its boiling point is 155 o.
- Its density is 1.405 g.ml-1.
- It is highly soluble in water. For instance, 142 g of thiourea can be dissolved in one litre of water at 25o.
- It is slightly acidic in nature
- Its crystals are highly combustible in contact with fire.
- It has pH value of more than 3.
- It is an odourless (with no smell) compound.
- Its surface tension is 1.04 10-2 N/m.
- Thiourea on heating above 130o , forms ammonium thiocyanate. Upon cooling it again converts into thiourea.
- Reduction – Peroxides get reduced into their corresponding Diols (chemical compounds with two hydroxyl groups) by thiourea. During this reduction reaction, a by-product formed which is called endo-peroxide. Endo-peroxide is a highly unstable compound.
- Due to its non - volatile nature, it is also used in the ozonolysis of cyclic alkenes to give carbonyl compounds.
- It reacts with alkyl halides and forms thiols.
Read more: Sulphur Dioxide
Chemical Information on Thiourea
[Click Here for Sample Questions]
Following is the Chemical Information on Thiourea:
| Density | 1.4 g/cm3 |
| Molecular Weight/ Molar Mass | 76.12 g/mol |
| Boiling Point | 150 – 160oC |
| Melting Point | 176 – 178oC |
| Chemical Formula | CS(NH2)2 |
Uses of Thiourea
[Click Here for Sample Questions]
Total global production of thiourea approximately 40% is produced in Germany and another 40% in China. About 10,000 tonnes of thiourea is being manufactured globally in a year. Its bulk production clearly proves its significance in the market. Few of its applications are listed below:
- Thiourea Dioxide (prepared by oxidation of Thiourea with Hydrogen peroxide) is used as a reducing agent in many chemical reactions used in textile processing.
- It is used in the production of flame-retardant resins, which prevents or slows down the spread of fires.
- It is used as a source of sulphide, a compound of sulphur with another element. It reacts with alkyl halides and changes them into thiols, a sulphur analogue of alcohols that is simple it is an organic compound consisting of compounds with a sulphur atom. For example, ethane – 1,2 – dithiol is prepared by 1,2 – dibromoethane. The reaction is given below:
C2H4Br2 + 2SC(NH2)2 → [C2H4(SC(NH2)2)2] Br2
[C2H4(SC(NH2)2)2] Br2 + 2KOH → C2H4(SH)2 + 2OC(NH2)2 + 2KBr
- Thiourea can be used as a source of sulphide in reactions with metal ions as well. For example, mercury sulphide is formed when mercury ion reacts with thiourea in presence of water and heat. The reaction is given below:
Hg2+ + SC(NH2)2 + H2O → HgS + OC(NH2)2 + 2H+
- Thiourea condenses with - dicarbonyl and forms pyrimidine derivatives. It is used in vulcanization accelerators.
- It is used as an auxiliary agent.
- It is used in silver – gelatine photographic prints, diazo paper, light-sensitive photocopy paper, etc.
- It is used in many electroplating processes such as Clifton – Philips and Beaver bright electroplating, etc.
- For copper printed circuits, tin (II) chloride solution is used. Thiourea is also used in the solution.
- It is used in silver cleaning products such as Tarn x which contains thiourea, sulfamic acid and detergent.
- It is used in gold and silver leaching. Lixiviants are used for this purpose and thiourea is an important ingredient of these. Lixiviant is a liquid medium used in hydrometallurgy to selectively extract the desired metal from the ore or mineral.
Read more: Sulphur Cycle
Health Hazards caused by Thiourea
[Click Here for Sample Questions]
Following are the Health Hazards caused by Thiourea:
- Even short exposure to the Thiourea causes severe irritation and temporary skin infection.
- 125mg/kg of thiourea can be deadly for rats on oral ingestion.
- On chronic exposure, thiourea can cause a goitrogenic effect on humans. Goitrogens can reduce the thyroid's ability to produce the hormones your body needs to function normally.
- Enlargement of the thyroid gland is known as goiter disease. In this disease, goitrogens disrupt the production of thyroid hormones. This stimulates the pituitary gland to release TSH and TSH promotes the growth of thyroid tissues.
Also Read:
| Related Articles | ||
|---|---|---|
| Organic Compounds | Electrochemical Cell | Organic Solvents |
Points to Remember
Following are some important points:
- Thiourea is an organosulfur compound which contain sulphur in it.
- There are two forms of Thiourea – Thione and Thiol.
- Melting point of thiourea is 182o.
- Boiling point of thiourea is 155o.
- Surface tension of thiourea is 1.04 10-2 N/m.
- It reacts with alkyl halides and forms thiols.
- 125mg/kg of thiourea can be deadly for rats on oral ingestion.
Sample Questions
Ques: What is thiourea used for? (2 Marks)
Ans: Industrial use of Thiourea includes the making of flame retardant resins and accelerators for vulcanization. Thiourea is used in the diazo paper as an auxiliary agent (light-sensitive photocopy paper) and almost every other form of copy paper. This is also used to colour the photographic prints in silver-gelatine.
Ques: Is thiourea a reducing agent? (2 Marks)
Ans: Thiourea dioxide (prepared by oxidation of Thiourea with Hydrogen peroxide) is a reducing agent that is stable in both solid form and cold aqueous solution. It displays a mild acidic reaction and only acquires maximum reduction capacity when subjected to heating up to approximately 100 ° C in an aqueous solution.
Ques: Which functional group is present in urea? (2 Marks)
Ans: The functional group (a group of atoms in a molecule with distinctive chemical properties, regardless of the other atoms in the molecule) in Urea is the carbonyl group. A functional group with a carbonyl group bound to 2 atoms of nitrogen, or a molecule containing the functional group. This simplest member of the family is also called urea.
Ques: Is urea acidic or basic? (2 Marks)
Ans: It is neither acidic nor alkaline when urea dissolves in water. This is used by our body in many ways, especially for the excretion of nitrogen. In the urea cycle, the liver shapes the urea by mixing two ammonia molecules (NH3) with a molecule of carbon dioxide (CO2).
Ques: What are thiourea drugs? (2 Marks)
Ans: Initially, Thiourea was the drug which was used to treat Graves' disease. Drugs of Second-generation have less toxicity which includes methimazole, carbimazole, and many more.
For Latest Updates on Upcoming Board Exams, Click Here: https://t.me/class_10_12_board_updates
Check-Out:
Comments